Current studies are designed to elucidate the structure, function and regulatory mechanisms of the active transport system for Na ion and K ion in excitable membranes. Immunochemical studies have shown that the glycoprotein subunit of the (Na ion plus K ion)-ATPase is closely associated with the ouabain-binding site of the enzyme. Transient kinetic studies have provided new and more direct evidence that the conformation of the transport ATPase is dependent upon the occupation of Na ion and K ion binding sites in addition to nucleotide binding and phosphorylation. An investigation of ouabain-sensitive cation fluxes in erythrocytes from subjects with myotonic dystrophy has found normal ratios of Na ion flux to K ion flux in contrast to a recently published report. Studies have been initiated in an effort to characterize endogenous tissue constituents that interact with the ouabain-receptor of the (Na ion plus K ion)-ATPase. BIBLIOGRAPHIC REFERENCES: Jean, D.H. and Albers, R.W.: Immunochemical studies on the large polypeptide of Electrophorus Electroplax (Na ion plus K ion)-ATPase. Biochem. Biophys. Acta. 452: 219-226, 1976. Jean, D.H. and Albers, R.W.: Molecular organization of subunits of electroplax (Na ion plus K ion)-activated ATPase. J. Biol. Chem. 252: 2450, 1977.